Preventing escape of GMO salmon

It’s been a long time coming. The FDA has finally released their decision about fast-growing, genetically engineered salmon. They state: “After an exhaustive and rigorous scientific review, FDA has arrived at the decision that AquAdvantage salmon is as safe to eat as any non-genetically engineered (GE) Atlantic salmon, and also as nutritious.” It may be safe to eat, but the remaining question is whether wild fish could be at risk from GMO salmon. Back in 2010, I combed through the FDA documents and scientific literature to find out. This post is a summary of the containment measures used for AquAdvantage salmon. See Risk assessment and mitigation of AquAdvantage salmon for the full details.

"Salmoneggskils" by en:User:Kils - en:Image:Salmoneggskils.jpg. Licensed under CC BY-SA 3.0 via Commons.
Atlantic salmon eggs by Hoenny via Wikipedia. AquAdvantage eggs will be prevented from entering the environment by a series of screens and filters.

When Aqua Bounty Technologies, Inc. applied to the FDA for approval of their AquAdvantage salmon, they were very specific about how and where the fish would be raised. The request was for one specific egg production facility in Canada and one specific fish production facility in Panama. The FDA’s approval is for these locations only, and a new approval would be needed for any new locations. Aqua Bounty selected these locations to have many overlapping ways to prevent release of GMO salmon into the environment. Aqua Bounty explains these containment methods in the environmental assessment that they submitted to the FDA. The containment methods are biological, physical, and environmental.

Biological containment

The most important way to prevent AquAdvantage salmon from breeding with wild salmon is to use only fish that can not breed (sterile fish). Most animals in nature have two copies of each chromosome. Fish eggs with three copies of each chromosome (called triploid) can be created by treating fertilized fish eggs with pressure, high temperatures, or certain chemicals. Resulting female fish are not able to produce eggs, so can not reproduce. Triploid fish are used all over the world as a way to prevent farmed or stocked fish from breeding. The pressure treatment used by Aqua Bounty results in at least 98% triploid fish (see page 57). Still, that’s up to 2% of fish that might be fertile, so they must be contained with other measures. To make matters a little more complex, some triploid males can still produce sperm. Aqua Bounty has reduced the risk of fertile fish escaping by using only female fish.

Physical containment

escape of GMO salmon would not result in environmental harm
Jumping salmon by Walter Baxter. AquAdvantage salmon will not be raised in an environment where they can exhibit this behavior.

Because a small percentage of AquAdvantage salmon could be capable of reproduction, additional containment methods are necessary. At both egg and fish production facilities, multiple layers of security will reduce risk of human sabotage.

These include on-facility living quarters for security personnel, security cameras, and 8’ chain link fencing around each property, among other measures. Both facilities use numerous layers of nets, screens, and filters.

At the egg production facility, chlorine is used in the drainage area to kill any eggs that escape filters. These containment methods mean less than 1% of fish could escape (see page 55), and keep in mind that 98% of fish are sterile so very few escapees have the potential to lay eggs. Still, it’s possible that the physical containment could fail (such as if a facility wasn’t maintained and all the nets and filters and screens failed) and release additional fish.

Environmental containment

In the highly unlikely case that a fertile AquAdvantage salmon escaped, Aqua Bounty has taken additional steps to further reduce the risk that any escaped fish could breed with sexually compatible male fish nearby.
The egg production facility is located in Prince Edward Island, Canada. The physical containment measures mean very few eggs could make it to nearby bodies of water.

Any eggs that did make it past the filters and chlorine would need to find a hospitable place to grow into adult fish. In the past, Atlantic salmon lived in this area, but over fishing, barriers to migration, and acid rain have made them locally extinct so any escaped eggs that managed to grow into adult female fish would not find a male to mate with. In the winter, temperatures in bodies of water near the facility are too low for salmon. Barriers to migration would prevent any escaped fish from moving out to sea during the summer. The eggs are raised in fresh water, and the relatively high salinity in the nearby river would further reduce likelihood of survival.

The fish production facility is located at a high altitude in Panama near a river that drains to the Pacific ocean. Much of the river water (up to 100% in the 4 to 5 month dry season) is used for power generation, and the canals that control water flow to power generation facilities are not suitable for salmon (see page 50). Dams provide a physical barrier to movement downstream. If any fish escaped and they managed to get past the barriers, they could survive in the river closest to the facility. If they try to move out to sea, though, the high temperatures in the lower lower parts of the river would kill salmon (see page 52). While escaped salmon might live in the upper river for a short time, they would not find any males to mate with, and escape to the Pacific ocean is very unlikely.

Worst case scenario

The multiple levels of containment makes it very unlikely that any AquAdvantage salmon could escape into the wild. However, despite all containment efforts, less than 1% of AquAdvantage salmon could escape from the rearing facility and, on average, 2% of the salmon will be diploids. Worst case scenario, that means 0.0002% of all fish reared (2 fish in every 10,000) could be fertile females that escape. These fish then face additional barriers to reproduction and spread of the gene that makes them grow faster than wild fish.

Atlantic salmon reach reproductive age between 1 and 4 years. Farmed salmon tend to reproduce earlier than wild fish, but even if an escaped fertilized egg could hatch, the young fish is unlikely to survive to reproductive age given that the environment near the egg production facility does not sustain salmon. Still, if escape were to happen and the escapee reached reproductive age, what would the result be?

The Atlantic salmon reproductive process requires fresh running water over a gravel bed. Salmon have complex mating and nesting behavior, and a male must be present when the female spawns. In the waters near the egg and fish rearing facilities, there are no males or gravel beds are available. If a female did manage to spawn, the lack of males means the eggs would not be fertilized. In addition, spawning takes so much energy that 60% or more female salmon die after spawning.

Past attempts have failed to reintroduce salmon to rivers near the egg facility and rainbow trout in the rivers near the fish facility. What if those rivers were suddenly able to sustain fish, perhaps due to climate change? Some trout and salmon species can interbreed, but generally produce sterile offspring, so there’s still very low likelihood of risk near the fish rearing facility.  The waters near the egg rearing facility present a little more likelihood of sustaining a sexually compatible salmon male. What would happen if a fertile AquAdvantage female made it to adulthood, was able to spawn, and those eggs were fertilized? More studies are needed on survival rates of fast growing vs wild type and on mixed populations, but research so far indicates low risk of harm.

All AquAvantage salmon carry only one copy of the gene sequence for fast growth, so if an escaped fertile AquAvantage salmon reached reproductive age and found a suitable mate, only one half of her offspring would carry the gene sequence. Those that carried the gene would, according to available research, be at a disadvantage to their siblings that did not.

Fast growing salmon are only able to grow fast if they have an easy food supply. Without extra food, they grow only slightly larger than wild fish. Salmon over expressing growth hormone under wild conditions have decreased swimming speed. Their reduced ability to swim away from predators or catch fish to eat means a higher death rate for fast growing salmon living in a natural environment.

Any advantage that fast growing fish might have over wild type fish will likely be cancelled out by negative effects. The gene for fast growth will either be eliminated from the wild population by natural selection or remain at a very low gene frequency, having minimal effect on the population. You may have seen studies that claim a gene for fast growth would spread through a wild population (the so-called Trojan fish theory). From what I’ve seen, those studies assume that the gene does not have negative effects – a very important factor when we’re talking about natural selection.

So even in the worst case scenario where every 2 in 10,000 raised fish escape and are fertile, they will quickly die in the nearby environment, and even if they manage to live to reproductive age they could not find a mate or a place to lay eggs, and even if they did manage to have offspring, those offspring would be at a disadvantage to wild fish, so the AquAdvantage gene would not spread.

Other risks

The FDA has found these salmon to be safe and nutritious. I’ve shown here that there is very little risk to wild salmon populations from AquAdvantage salmon escapes. What about other risks – particularly economic ones?

Additional salmon on the market will affect the wild salmon fishing industry, the farmed salmon industry, and the tax revenues to the states that support those industries. Representatives of the wild salmon fishing industry have expressed concern about escape of farmed salmon, but that concern doesn’t apply to AquAdvantage salmon which are raised in a very controlled environment.

Escapes from other fish farms may pose a risk, but that is not a reason to block AquAdvantage. In fact, if AquAdvantage outcompetes other fish farming (such as sea pens) then AquAdvantage might help reduce those other methods – so you can see why the farmed salmon industry might be concerned.

If fearmongering about AquAdvantage salmon continues, people might turn away from farmed fish entirely. This could have a negative effect on the farmed fish industry, and could also have a negative impact on wild fisheries if more wild fish are harvested, and could have a negative impact by removing healthy farmed fish from people’s diets. Of course, these are risks of fearmongering, not risks of AquAdvantage salmon.


  1. By far the most likely way for a GMO salmon to interbreed with the wild population is if a human being is determined to obtain fertile salmon from the breeding population and release them into the wild. The whole matter of regulation is completely irrelevant to preventing such obviously illegal behavior. Nothig but politics can explain why this regulatory process took so many years.

  2. One of the really interesting twists in this drama was the “trojan” salmon theory. Activists used this to scare people. However, the author of that work–William Muir–also showed that these salmon won’t accomplish it. I wrote about that fairly recently (it was not well covered in the mainstream press, ahem…):
    And I’ve seen Muir quoted in most of the GMO salmon approval pieces I’ve read, supporting the fish. So activists can’t keep using his old theory.
    Science. It works.

  3. If they escape, just make sure they don’t get a hold of any motorcycles and we’ll be fine. 🙂

  4. In this case, I am sure they will. They’ll be sold under the AquaBounty brand. That means they are these specific GM salmon.

  5. The main problem with the claim is that the salmon variety being discussed has triploid chromosomes. It’s sterile because of having an uneven amount. I was speaking to someone about it yesterday.
    Honestly, I was skeptical of approving the GE salmon at one point until learning that it cannot reproduce in normal conditions due to the extra set of chromosomes.

  6. I think it’s already done. I was wrong about the brand, though. It’s AquAdvantage. That trademark is already registered and in all of the press releases they keep referring to it as “Aquadvantage Salmon”.

  7. I really love that post of yours. I feel silly – I recalled your post but couldn’t remember where I saw it, and it turns out it was on the Biofortified Blog lol.

  8. It doesn’t matter if the activists get their way and ban it from stores. They are preventing folks from having the choice of this enviro-friendly option.
    Already there’s a lawsuit to block it from everyone too.
    Labels are a red herring. So to speak.

  9. It struck me today that people are also confused on the triploid fish issue. I think lot of people don’t know that this is a widely-used strategy to make fish for stocking ponds and lakes. The State of Alaska has a good page explaining triploid fish stocking, and how and why they use it as a conservation measure: Click the tab for the triploid FAQ.

    Are triploid fish safe to eat?
    Yes. Triploid fish have been produced for sport fishing and commercial use for over 20 years. Local grocers sell triploid Atlantic salmon and rainbow trout. Triploid production is common not only with fish, but also in many other foods found in our grocery stores. Examples of common triploid food items include all bananas and seedless watermelons.

  10. It seems to me that the most likely risk is someone deliberately releasing a fertile version of the fish purposely to break AquaAdvantage’s market advantage. The more successful they become the more likely this will be the result.

  11. This technology isn’t going to stop, and realistically, many more companies are going to do their own versions. There will not always be so many safeguards taken, that’s the rub. IMHO

  12. David, the original breeding stock of GMO salmon are not triploid. The company has maintained and will continue to maintain diploid salmon to produce eggs, and the eggs are then processed to become triploid. There will always be a stock of fertile GMO salmon and therefore there is always the possibility that some irresponsible person could purposely release them.

  13. The really simple answer is that this is a substantial domestication of salmon. Just like escaped Butterball Turkeys™ don’t outcompete wild fowl, they are not going to out compete wild salmon – they will get very hungry, and then very tired, and then they will starve in the winter when their growth hormone is still set to 10 and they can’t find enough food.

  14. It is other cases we are concerned about. More companies will be doing this and likely will shortcut the precautions somewhere. What could possibly go wrong??? Or rather, what will likely go wrong??

  15. Yes, and we should put a lot of effort into increasing the effectiveness of FDA to help clear an even more sane path into a food supply future.

  16. It is not so much fear of the unknown, but learning how better to approach and explore the unknown….

  17. No, but it does take FDA AND some outside checks and balances to clarify the science from the politics involved. To the degree the politics creeps in, the quality of the science degrades.

  18. Outside checks… You mean like the USDA, EPA, company science, university science other nation’s regulatory bodies and the media constantly investigating anything that looks fishy?

  19. Yes, very much so, but they often overlook important areas that need looking into because of political biases to avoid making waves. There are very many areas of water quality and human toxicology issues that EPA, and the other agencies and institutions, carefully avoid at all costs to investigate as public health risks (even though there is already plenty of science pointing out the need.

  20. Carefully avoid, huh? Sounds like you got this all figured out. I assume you have the evidence to show that these are being avoided as you suggest?

  21. Since we are talking about salmon and eating salmon, I’ll give an example of the gross inadequacy often seen in the regulatory system we are considering concerning food safety and how it relates to medical and societal harm. A typical salmon fishing person has a tackle box to carry equipment necessary for the task, complete with lures, reels, fishlines and sinkers. Often a boat is used. When open up my box to set up the fishing pole, I reach for leaders, lures and sinkers. Most tackle boxes have built up a fine black metallic powder caused by lead sinkers rolling around in the box. This powder is almost pure lead. Wet hands get contaminated, gear gets contaminated, sandwiches, apples, cooler ice, boat bottoms, and fish mucus become toxic metal sources for exposures that repeatedly bring exposures home to the family when fish are thrown into the frying pan. The whole family gets dosed. Hundreds of scientific researchers can attest to the accuracy of the toxicologic risks involved …. and shake their heads in disbelief that in this day and age where gasoline lead, leaded house paint, and lead in water pipes have been banned from use… we still allow our regulatory agencies to avoid looking at this blatant fishing methodology use of lead to poison vast numbers of society. Fear of NRA, mining, and industry lobbies pushing congress to keep EPA and other agencies from recognizing this toxic pollution allows it to continue in spite of all of the research. That, does not even begin to correct the ecotoxicologic craziness of dumping all this lead directly into low hardness waters that poison whole aquatic systems… while we spend many millions of dollars to try to restore salmon habitat and numbers. There are alternative, less toxic sinkers manufactured, so we would not have to poison our families or the salmon. Crazy, crazy, regulatory politics and subsequent massive societal harm. Only one example of the type of regulatory blinders that are threatening adequate over site other food industry social/political BS. IMHO

  22. So, where does NEPA avoid to adequately deal with the lead fishing sinker pollution scenarios described in the post above? Politics trumps the science.. over and over again. That is why I’m skeptical of adequate regulatory influence in determining safety adequacy for GMO/GE technology. FDA is not immune to the political biases, just like EPA is not able to do due diligence in similar regulatory work. These agencies cannot accomplish their mandated missions unless they become truly supported in doing so by industry and Congress.

  23. Most people questioning GMO/GE tech have brains, and many have significant scientific backgrounds, but many try rather ineffectively to rail against all GE because they are caught up in the political nature of the regulatory process, causing politics to once again overshadow the science. However, there are many that are more thoughtful and do not want to throw out the baby with the bathwater… they just want to help the science progress without so much political intrusion. There is plenty of politics on both sides polarizing the discussions. To the degree both sides buy into the polarization, and badmouth each other… science is harmed and we have lost opportunity for advancing.

  24. Great little story, but what I asked for was evidence that (I quote) “… EPA, and the other agencies and institutions, carefully avoid at all costs to investigate as public health risks”
    Besides…commercial salmo fisheries use nets, not poles & sinkers. But nice try.

  25. The pressure treatment used by Aqua Bounty results in at least 98% triploid fish (see page 57). Still, that’s up to 2% of fish that might be fertile, so they must be contained with other measures.

    I understand that flow cytometry is also used to detect ploidy so that the 2% diploid eggs can be eliminated.

    Ploidy of the salmon is routinely determined by flow cytometric analysis of propidium iodide-stained erythrocytes. For the large-scale production of triploid salmon it would be advantageous to have the ability to assess ploidy as early in development as possible. To this end, a series of studies were conducted to develop a procedure for flow cytometric determination of ploidy from fertilized egg samples, and to employ the procedure to validate the conditions used to generate triploid AquAdvantage Salmon.
    It would be nice to get confirmation that this is done as a matter of course.

  26. Are you sure that’s the case? Is it AquaAdvantage’s business plan to provide identity preserved, packaged salmon end products to the retail marketplace? I believe its goal is to provide fish stocks to growers who would provide raw grown salmon to processors at the wholesale and retail level, but not necessarily as a branded AquaAdvantage product. Maybe I am wrong.

  27. I could be wrong as well. I was basing these assumptions off of every news release showing the AquAdvantage registered brand name. As you said, that could be a wholesaler brand, though.

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